this one will be used to help test new rules, new hosts, etc. for TSC.

Hosting isn't easy, so a couple of the vet hosts decided that having a group in which people who want to try hosting can practice hosting a TSC or 2 in order to get acquainted with the system. Some people might be intimidated by hosting here and might not want to go on and host a full TSC. Some people might want to host a TSC, but might not be able to host well enough. At the end of each of the TSCb the participants will get a questionaire to fill out (it'll be only a couple short questions). This will provide critiques and criticisms for the potential host as well as give the hosting committee access to information that they might not have seen (Let's face it, people tend to be nicer to the people who are judging them over the rest of the pack).

As the TSCb group description says

"Tengaged Song Contest: The place to discover new music and showcase your individual music tastes!
Tengaged Song Contest BETA: The place to test out new things for TSC (new hosts, new rules, etc.)"

oh i see! its all become clear now, thank you